Heating stove



Aug. 23, 1932. KAHN I 1,873,767

HEATING STOVE Filed 001;. 8, 1930 2 Sheets-Sheet 2 gnuwntoa anointPatented Aug. .23, 1932 umreo STATES PATENT. oF'ri-cE nnnrnmn ammo);cmcnnu'rr, onro, ASSIGNOB 'ro THE ESTATE STOVE courm, or mnrou. .oruo, Aconrona'rrou or 01110 1 nm'rme srovn. 7

Application filed October a, 1930. Serial K0. aaaaio.

This invention relates to heaters, and more particularly to portableheaters of the convection type.

One of the principal. ob'ects of the inven- 5 tion is to provide such aeater with means for increasing the effectiveness and efliciency of thetransfer of heat energy into the circulated air during operation and forincreasing the life of the heater,'and its ability to withstandabnormally hard operation.

Another object of the invention is the provision in such a heater, of anair heating duct of high thermal conductance, in.which the exteriorsurface is the heat absorbing surface, and the interior, heattransferring surface, has substantially greater area than the exteriorabsorbing surface. 7

Other objects and advantages of the invention will be apparent from thefollowing description, the attached drawings and the appended claims.

In the drawings, which disclose a preferred embodiment of the invention,

Fig. 1 is a vertical sectional view of a heater constructed inaccordance with this invention; and

Fig. 2 is an enlarged view, partly in section, of the air heating duct.

Referring now to the drawings, in which like characters of referencedesignate like parts throughout the several views thereof, the inventionis shown and described as embodied in a portable heater of theconvection type adapted to utilize coal or other solid fuel, such as isadapted for use in a living room or the like to heat the air thereinprimarily by convection. A heater of this character is such a one as issold under the mark Heatrola. The heater comprises generally an innerstructure within which a fire may be maintained,'and an enclosing casingin which suitable openings are provided for the passage of air to beheated by contact with the heated walls of the enclosed and enclosingstructure. An air heating duct is associated with the enclosed structureto provide an efiicient means of heat transfer and to thereby increasethe circulation of air through the heater. The heater .comprises a basemember 10 having suitable supporting feet 11; the base providingasupporting means for the enclosing cas ng, and also-for the enclosed orinner heating structure which comprises an ash box 12 which, as shown, 1

may be formed as an integral part of the base 10 or may be a separatepiece attached thereto by suitable means. The ash box has mounted uponit a fire-pot 1 1; a suitable grate 15 being provided therein for thesupport of a fuel bed. A combustion chamber 16 is provided by anenclosing member 17 which is attached to the top of the fire b0x as bymeans of bolts 18; a suitable flue outlet 19 being provided adjacentthetop of the combustion chamber 16. The exterior of the combustionchamber casing 17 carries' ribs 20, and similar ribs 21 are on theexterior of the fire-pot 14 to facilitate the trans.- fer of heat fromthe hot walls-of the heating structure to air which is adapted tocirculate over the outer surface of this structure. enclosing casingcomprises vertically extending walls 22 suitably joined, and supportedat 23 upon the base 10. The casing walls 22 are suitably spaced from theheating elements to provide an air space or flue 25 throu h which airmay pass upwardly, being heate as it passes in contact with the heatedwalls of this air circulating space. The casing walls are provided witha plurality of louvers 24 adjacent the base 10, which admit air into thecirculating space, at the same time preventing [direct outward radiationfrom the heating structure while allowing a certain amount of radiationdownwardly to warm the floor around the heater. Air which is heatedwithin the area 25 rises and passes from the heater through a perforatecover member 26 suitably supported by the members 27 the cover providinga cap for the casing walls 22 and providing an outlet for the heated airthrough a plurality of openings 28 of sufficiently large proportions topermit of rapid egress of large quantities of rapidly moving airtherethrough, tothus create a circulation of high veloclty so that theheated air has the power to travel through a large area such as anentire house, which may be thus effectively heated and maintained at auniform temperature.

The

i To provide for additional transfer of heat from'the hot products ofcombustion'w-ithin the combustion chamber 16 to the air passing throughthe ace25 an air heating duct 30 .is provided within the upper-portionof the combustion chamber 16 ad acent the flue outlet 19 through whichheated air from the space 25 may pass to be further-heated by contactwith the hot inner surface of the walls of the duct and be thendischarged through the ro es of theheater at relatively high velocity.The air heating duct 30 in-.

creases the heating effect upon the circulatin air, and correspondinglyiIICREaSGS the ive ocity of the air passing through t e' heater and sogreatly increases the rate of circulation thereof and accelerates thecirculation of air through the room.

As shown the air heating duct 30 comprises a hollow invertedsubstantially T -shaped metallic casing made preferably as an ironcasting, and which is directly exposed to the hot products ofcombustionin the interior of the combustion chamber. The duct 30100111-rises oppositely extending open-ended branches 31 which project throughopenings 32 in the side walls ofthe combustion chamber casing 17 andopen into the area. 25, and an open-ended upstanding portion 33 which isattached within the top of the combustion chamber adjacent an opening 34provided therein. Air which enters the branches olding bolts 39 whichpass through the casing 17 and are adapted to'hold the air heating duct30 in position with respect} to the combustion chamber. A suitablesealing material, such as cement, may be inserted in the space 40between the rim 35 and the engaging rim 36 to provide a gas tight joint.

' 'table sealing means are also provided be tween the. pro ectin ends ofthe air duct branches 31 where t ey extend through the openings 32 inthe side walls of the combustion chamber casing 17 'As shown, thesealing means at each opening 32 comprises tworing like members whichloosely encircle the duct end 31, the inner ring 42 being provided withan annular depression 43 which is adapted to receive suitable packingmaterial such as asbestos rope, while the outer ring 45 l is ada ted tooverlie the rin 42 to com ress I fies g P theas tos rope in the groove43 against the duct and provideatight but resilientj oint with thesurface of the duct end 31. The rings 42 and 45 are provided withattaching means such as the similarly positioned ears 47 havingopeningsthrough which bolts 48'pass for the attachment of the rings to thecombustion chamber. In assembling the sealing rings the contactingsurfaces between the rings and the combustion chamber may be cemented sothat upon drawing the bolts 48 up tight, gas tightstuffing boxes will beprovided within which each end 31 ofthe air duct may freely expand andcontract under the influence of temperature change Without placing anystrains on the structure itself.

The duct 30, being positioned within the combustion zone,- is subjectedto very high temperatures. The lower portion is positioned so. that theflames of combustion impinge directly thereon. The upstanding portion 32of the duct is positioned in the top of the combustion chamber andadjacent the flue, but it too is subjected to high temperatures andhighly heated products of combustion. As a result the duct absorbslargev quantities of heat energy on its outer absorbing side which ittransfers to the air currents passing therethrough. The duct thereforenot only increases the efficiency of the heater by increasing the rateof air circulation but also provides an economy of fuel consumption bytransferring to useful purpose heat which would otherwise be wasted bybeing discharged from the flue. The interior or heat transferringsurface of the duct is formed to have an area for contact with the airwhich is greater than the exterior heat absorbing surface of-the duct.As shown, the interior surface 50 of the air duct is provided withV-shaped ribs positioned substantially transversely to the flow of airthrough the duct; the outside surface being left smooth:

As-shown the ribs in the several parts of the duct are differentlydirected, the ribs in the body portion being angularly arranged withrespect to ribs in the branches, the ribs in the various parts of theduct being thus all positioned transversely to the path of thecirculating air. The proportions are such that the interior heattransferring or radiating surface is of greater area than the exteriorheat absorbing surface, whereby the transfer of heat from the productsof combustion to the interior surface of the duct and thence through theduct and into the air passing thereover is accomplished with greatlymcreased effectiveness.

The duct 30 is positioned to be impinged on by the very hot products ofthe combustion. Itis not unusual for ducts of the character previouslysometimes used to be heated to incandescence, to-temperatures of theorder of 1300 F. By the use of this invention, using a preponderatingheat transferring surface, the absorption of heat I creasing theconductivity as tocause rapid burning out of the duct. However, in-th1sinvention due to the increasedheat transfer 1 T creases, at

tial across the duct wall. This results in a material increase in heattransfer and, at the same time, a decreased temperature of the duct wallitself. The thermal conductivity of iron decreases as the temperaturetemperature of the duct would ordinarily have reached red heat under rthus result, especially under severe condl f tions of heavy load, wouldresult in so dethe temperature of the duct walls is kept down by therapid transferring ofthe heat absorbed so that the wall temperature willnot reach a point which will inefiicient' transfer of heat or resu ingdown from overheatin the natural inefliciency o the material at hightemperatures which, in the case of iron at 1300 F. produces red hea't,volumes of air passing over red hot iron causes a rapid oxidation of thesurface and quickly forms a resistin coating which further andpermanently ecreases the heat transferring capacity of the duct;an'dwill cause burning out of the duct. j

While the form of ap aratus herein described constitutes apreferred-embodiment of the invention, it is to be understood that theinvention is not limited to this precise form of apparatus, and thatchanges may be made therein without departing from the scope of theinvention which is defined in the appended claims. 7 What is claimedis: 1. In a heater of the character described, in which a combustiblefuel is burned within a combustion chamber, and convection air is passedover heat transferring surfaces heated by the combustion within saidchamber; an air heating duct having an exterior heat absorbing surfacepositioned within the path of the heated products of combustion toreceive heat ener therefrom, and an produce an t in breakinterior heattransferring surface positioned in the path of travel of the air beingheated and in heat energy transferring relation with said traveling air,said heat transferring surface being formed of closely positionedcorrugations to resent an efiece tive heat transferring su'r ace whichis of greater extent than the said heat absorbing surface, and formingwith-the heat absorbing surface a substantially uniform path ofconduction.

2. In a heater of the character described,

red heat having become almost negligible; and in previously used ductsthe;

ther heavy. draft. The high temperature wh h would In addition to acombustionfchamber,and convection air is passed over heat transferringsurfaces heated b the combustion within saidchamber; an air heatin ducthaving anexterior heat in which a combustible fuel is burned within Iabsorbing s'ur ace ositioned within the path of the heated prouctsofcombustion to receive heatenergy the'r'efrom,'and an interior heat-transferrin "surface osi'tioned in the traveling air said heattransferring surface being forme ofclosely positione shallowcorrugationsto present a grooved-interior aside n efl'ective heat transferringsurabsorbing surface, and to form with the heat absorbing surface a heatconduction wall in which the path of maximum len h doesnot substantial yexceed the path 0 conduction of minimum length.

3. In a heater of the character described, in which a combustible fuelis burned within acombustion chamber, and convection air is passed overheat transferring surfaces heated by the combustion within said chamber;an air heating duct having an exterior "heat absorbing surfacepositioned within the'path of the heated products of combustion toreceive heatenergy therefrom, and an interior heat transferring surface.positioned in the path of travel of the air being heated and in heatenergy transferring relation with said traveling air, said heattransferring surface being formed of closely positioned corrugations topresent a path of travel 0 the air bemg heated and in cat energytransferring relation with said heat transferring surface constructed topro-.

whichis of greater extent than the said heat 7 grooved interior heattransferring surface,

greater extent than the said heat absorbing surface.

4. In a heater of the character described, 1

in which a combustible fuel is burned within a combustion chamber, andconvection air is passed over heat transferring surfaces heated by thecombustion within said chamber; a curved air heating duct having asmooth exterior heat absorbing surface positioned within the path of theheated products of combustion to receive heat energy therefrom, and aninterior heat transferring surface positio'nedin the path of travel ofthe air being heated and in heat energy transferring relation with saidtraveling air, said heat transferringsurface being formed of closelypositioned shallow corrugations to present a'grooved interior heattransferring surface, the grooves and intermediate ribs in the severalparts of the said interior surface-being arranged angularlywith respectand substantially transverse to the direction of air flow therethrough,the said duct being constructed to provide an effective heat transferrinsurface which is of greater extent than t e said heat absorbing surface.

5. In a heater of the character described, in which a combustible fuelis burned within a combustion chamber, and convection air is passed'over heat transferring surfaces heated by the combustion within saidchamber; an air heating duct for the most part of v substantiallytubular cross section and comprising a wall of substantially uniformheat conducting characteristics, said duct having a body portion andlaterally extending branches, and having an exterior heat absorbingsurface positioned within the path of the heated products of combustionto receive heat energy therefrom, and aninterior heat transferringsurface positioned in the path oftravel of the air being heated and in.heat energy transferring relation with said traveling air, said heattransferring surface being formed of circularly extending closelypositioned shallow grooves to present an effective heat transferringsurface which is of greater extent than the 'said heat absorbingsurface. v

In testimony whereof I hereto afiix my signature. v

BERTRAND B. KAHN.

